Graphene oxide nanoribbons (GONRs) as pH-tolerant electrodes for supercapacitors: Effect of charge carriers and loading

Global energy consumption is increasing, which is driving up demand for improved energy storage technologies. Supercapacitors have attracted a lot of attention because of their fast charging and discharging rate, high power density, and long-term cycling stability when compared to regular batteries. Graphene oxide nanoribbons (GONRs) have garnered significant attention recently due to their unique ultrathin two-dimensional structure characteristics, making them a promising material for electrochemical energy storage devices such as supercapacitors. This study evaluates the supercapacitance behavior of graphene oxide nanoribbons (GONRs) resulting from oxidative longitudinal unzipping of multi-walled carbon nanotubes (MWCNTs) via chemical oxidation. The following techniques were used to assess the changes: Raman spectroscopy, XPS, TEM, FT -IR, XRD, and EDS. GONR's supercapacitive behavior was thoroughly investigated using different loadings and evaluation systems (three and two-electrode systems) in a range of media (H2SO4, KOH, Li2SO4, and K2SO4). GONRs demonstrated good stability, maintaining approximate to 100 % of their efficiency and capacitance at a high current density of 10 A/g even after 10,000 cycles, a broad potential window (up to 1.7 V), and a relatively high capacitance (approximately 400-800 F/g) in all tested electrolytes making it a universal electrode suitable for all types of aqueous-based electrolytes. The effects of charge carriers, electrolyte pH, and material loading are found to have a significant impact on the specific capacitance of GONRs. As a cationic charge carrier, H+ is found to be superior to Li+ and K+, with Li+ and K+ not significantly different. However, it is discovered that as an anionic charge carrier, OH- is superior to SO42-. Overall, H2SO4 was discovered to be the best electrolyte for GONRs, even at high material loading, because it recorded the highest supercapacitance in both two- and three-electrode systems, using a combination of electrical double layer and pseudo-capacitive mechanisms. Increasing the loading of the GONRs is found to reduce their capacitance, and hence further modifications to prevent the GONRs stacking are needed. The reported specific capacitance for the highly loaded GONRs is higher than that of the previously reported values for GO or RGO.